1. Field of the Invention
The invention relates to binding proteins that bind to insulin-like growth factor-2 (IGF-II) with cross-reactivity to insulin-like growth factor-1 (IGF-I) and uses of such binding proteins. More specifically, the invention relates to monoclonal antibodies directed to IGF-II with cross-reactivity to IGF-I and uses of these antibodies. Aspects of the invention also relate to hybridomas or other cell lines expressing such antibodies.
2. Description of the Related Art
Insulin-like growth factor IGF-I and IGF-II are small polypeptides involved in regulating cell proliferation, survival, differentiation and transformation. IGFs exert their various actions by primarily interacting with a specific cell surface receptor, the IGF-I receptor (IGF-IR) and activating various intracellular signaling cascades. IGFs circulate in serum mostly bound to IGF-binding proteins (IGFBP-1 to 6). The interaction of IGFs with the IGF-IR is regulated by the IGFBPs, and IGFs can only bind to the IGF-IR once released from the IGFBPs (mostly by proteolysis of the IGFBPs). IGF-I can also bind to a hybrid receptor comprised of IGF-IR and insulin receptor (IR) subunits. IGF-II has been shown to bind to the “A” isoform of the insulin receptor.
Malignant transformation involves the imbalance of diverse processes such as cell growth, differentiation, apoptosis, and transformation. IGF-I and IGF-II have been implicated in the pathophysiology of a wide range of conditions, and are thought to play a role in tumorigenesis due to the mitogenic and antiapoptotic properties mediated by the receptor IGF-IR. LeRoith and Roberts, Cancer Lett. 195:127-137 (2003).
IGF-I was discovered as a growth factor produced by the liver under the regulatory control of pituitary growth hormone and was originally designated somatomedin-C. Salmon et al., J. Lab. Clin. Med. 49:825-826 (1957). Both IGF-I and IGF-II are expressed ubiquitously and act as endocrine, paracrine, and autocrine growth factors, through their interaction with the IGF-IR, a trans-membrane tyrosine kinase that is structurally and functionally related to the insulin receptor (IR). IGF-I functions primarily by activating the IGF-IR, whereas IGF-II can act through either the IGF-IR or through the IR-A isoform. LeRoith and Roberts, Cancer Lett. 195:127-137 (2003). Additionally, the interaction of both IGF-I and IGF-II with the IGF-binding proteins may affect the half-life and bioavailability of the IGFs, as well as their direct interaction with receptors in some cases. Rajaram et al., Endocr. Rev. 18:801-831 (1997).
IGF-I has a long-term impact on cell proliferation, differentiation, and apoptosis. Experiments in cultured osteosarcoma and breast cancer cells suggested that IGF-I is a potent mitogen and exerts its mitogenic action by increasing DNA synthesis and by stimulating the expression of cyclin DI, which accelerates progression of the cell cycle from G1 to S phase. Furlanetto et al., Mol. Endocrinol. 8:510-517 (1994); Dufourny et al., J. Biol. Chem. 272:311663-31171 (1997). Suppression of cyclin D1 expression in pancreatic cancer cells abolished the mitogenic effect of IGF-I. Kornmann et al., J. Clin. Invest. 101:344-352 (1998). In addition to stimulating cell cycle progression, IGF-I also inhibits apoptosis. IGF-I was shown to stimulate the expression of Bcl proteins and to suppress expression of Bax, which results in an increase in the relative amount of the Bcl/Bax heterodimer, thereby blocking initiation of the apoptotic pathway. Minshall et al., J. Immunol. 159:1225-1232 (1997); Parrizas et al., Endocrinology 138:1355-1358 (1997); Wang et al., Endocrinology 139:1354-1360 (1998).
Like IGF-I, IGF-II also has mitogenic and antiapoptotic actions and regulates cell proliferation and differentiation. Compared with IGF-I, high concentrations of IGF-II circulate in serum. High serum IGF-II concentrations have been found in patients with colorectal cancer, with a trend towards higher concentrations in advanced disease. Renehan et al., Br. J. Cancer 83:1344-1350. Additionally, most primary tumors and transformed cell lines overexpress IGF-II MRNA and protein. Werner and LeRoith Adv. Cancer Res. 68:183-223 (1996). Overexpression of IGF-II in colon cancer is associated with an aggressive phenotype, and the loss of imprinting (loss of allele-specific expression) of the IGF-II gene may be important in colorectal carcinogenesis. Michell et al., Br. J. Cancer 76:60-66 (1997); Takano et al., Oncology 59:210-216 (2000). Cancer cells with a strong tendency to metastasize have four-fold higher levels of IGF-II expression than those cells with a low ability to metastasize. Guerra et al., Int. J. Cancer 65:812-820 (1996).
Research and clinical studies have highlighted the role of the IGF family members in the development, maintenance and progression of cancer. Many cancer cells have been shown to overexpress the IGF-IR and/or the IGF ligands. For example, IGF-I and IGF-II are strong mitogens for a wide variety of cancer cell lines, including sarcoma, leukemia, and cancers of the prostate, breast, lung, colon, stomach, esophagus, liver, pancreas, kidney, thyroid, brain, ovary, and uterus. Macaulay et al., Br. J. Cancer 65:311-320 (1992); Oku et al., Anticancer Res. 11: 1591-1595 (1991); LeRoith et al., Ann. Intern. Med. 122:54-59 (1995); Yaginuma et al., Oncology 54:502-507 (1997); Singh et al., Endocrinology 137:1764-1774 (1996); Frostad et al., Eur. J. Haematol 62:191-198 (1999). When IGF-I was administered to malignant colon cancer cells, they became resistant to cytokine-induced apoptosis. Remacle-Bonnet et al., Cancer Res. 60:2007-2017 (2000).
The role of IGFs in cancer is also supported by epidemiologic studies, which showed that high levels of circulating IGF-I and low levels of IGFBP-3 are associated with an increased risk for development of several common cancers (prostate, breast, colorectal and lung). Mantzoros et al., Br. J. Cancer 76:1115-1118 (1997); Hankinson et al., Lancet 351:1393-1396 (1998); Ma et al., J. Natl. Cancer Inst. 91:620-625 (1999); Karasik et al., J. Clin. Endocrinol Metab. 78:271-276 (1994). These results suggest that IGF-I and IGF-II act as powerful mitogenic and anti-apoptotic signals, and that their overexpression correlates with poor prognosis in patients with several types of cancer.
Using knockout mouse models, several studies have further established the role of IGFs in tumor growth. With the development of the technology for tissue specific, conditional gene deletion, a mouse model of liver IGF-I deficiency (LID) was developed. Liver-specific deletion of the igf1 gene abrogated expression of IGF-I mRNA and caused a dramatic reduction in circulating IGF-I levels. Yakar. et al., Proc. Natl. Acad. Sci. USA 96:7324-7329 (1999). When mammary tumors were induced in the LID mouse, reduced circulating IGF-1 levels resulted in significant reductions in cancer development, growth, and metastases, whereas increased circulating IGF-1 levels were associated with enhanced tumor growth. Wu et al., Cancer Res. 63:4384-4388 (2003).
Several papers have reported that inhibition of IGF-IR expression and/or signaling leads to inhibition of tumor growth, both in vitro and in vivo. Inhibition of IGF signaling has also been shown to increase the susceptibility of tumor cells to chemotherapeutic agents. A variety of strategies (antisense oligonucleotides, soluble receptor, inhibitory peptides, dominant negative receptor mutants, small molecules inhibiting the kinase activity and anti-hIGF-IR antibodies) have been developed to inhibit the IGF-IR signaling pathway in tumor cells. One approach has been to target the kinase activity of IGF-IR with small molecule inhibitors. Two compounds were recently identified as small molecule kinase inhibitors capable of selectively inhibiting the IGF-IR. Garcia-Echeverria et al., Cancer Cell 5:231-239 (2004); Mitsiades et al., Cancer Cell 5:221-230 (2004). Inhibition of IGF-IR kinase activity abrogated IGF-I-mediated survival and colony formation in soft agar of MCF-7 human breast cancer cells. Garcia-Echeverria et al., Cancer Cell 5:231-239 (2004). When an IGF-IR kinase inhibitor was administered to mice bearing tumor xenografts, IGF-IR signaling in tumor xenografts was inhibited and the growth of IGF-IR-driven fibrosarcomas was significantly reduced. Garcia-Echeverria et al., Cancer Cell 5:231-239 (2004). A similar effect was observed on hematologic malignancies, especially multiple myeloma. In multiple myeloma cells, a small molecule IGF-IR kinase inhibitor demonstrated a >16-fold greater potency against the IGF-1R, as compared to the insulin receptor, and was similarly effective in inhibiting cell growth and survival. Mitsiades et al., Cancer Cell 5:221-230 (2004). The same compound was injected intraperitoneally into mice and inhibited multiple myeloma cell growth and enhanced survival of the mice. Mitsiades et al., Cancer Cell 5:221-230 (2004). When combined with other chemotherapeutics at subtherapeutic doses, inhibition of IGF-IR kinase activity synergistically reduced tumor burden. Mitsiades et al., Cancer Cell 5:221-230 (2004).
Another approach to inhibit IGF signaling has been the development of neutralizing antibodies directed against the receptor IGF-IR. Various groups have developed antibodies to IGF-IR that inhibit receptor IGF-I-stimulated autophosphorylation, induce receptor internalization and degradation, and reduce proliferation and survival of diverse human cancer cell lines. Hailey et al., Mol Cancer Ther. 1:1349-1353 (2002); Maloney et al., Cancer Res. 63:5073-5083 (2003); Benini et al., Clin. Cancer Res. 7:1790-1797 (2001); Burtrum et al., Cancer Res. 63:8912-8921 (2003). Additionally, in xenograft tumor models, IGF-IR blockade resulted in significant growth inhibition of breast, renal and pancreatic tumors in vivo. Burtrum et al., Cancer Res. 63:8912-8921 (2003); Maloney et al., Cancer Res. 63:5073-5083 (2003). Experiments utilizing chimeric humanized IGF-IR antibodies yielded similar results, inhibiting growth of breast cancer cells in vitro and in tumor xenografts. Sachdev et al., Cancer Res. 63:627-635 (2003). Other humanized IGF-IR antibodies blocked IGF-I-induced tyrosine phosphorylation and growth inhibition in breast and non small cell lung tumors, as well as in vivo. Cohen et al., Clin. Cancer Res. 11:2063-2073 (2005); Goetsch et al., Int. J. Cancer 113:316-328 (2005).
Increased IGF-I levels have also been associated with several non-cancerous pathological conditions, including acromegaly and gigantism (Barkan, Cleveland Clin. J. Med. 65: 343, 347-349, 1998), while abnormal IGF-I/IGF-II receptor function has been implicated in psoriasis (Wraight et al., Nat. Biotech. 18: 521-526, 2000), atherosclerosis and smooth muscle restenosis of blood vessels following angioplasty (Bayes-Genis et al., Circ. Res. 86: 125-130, 2000). Increased IGF-I levels have been implicated in diabetes or in complications associated with diabetes, such as microvascular proliferation (Smith et al., Nat. Med. 5: 1390-1395, 1999).
Antibodies to IGF-I and IGF-II have been disclosed in the art. See, for example, Goya et al., Cancer Res. 64:6252-6258 (2004); Miyamoto et al., Clin. Cancer Res. 11:3494-3502 (2005). Additionally, see WO 05/18671, WO 05/28515 and WO 03/93317.